Method and apparatus for injecting steam into subsurface formations



July 28 1954 T. M. DoscHER METHOD AND APPARATUS FOR INJECTING STEAM INT0 suBsuRFAcE FORMATIONS Fild July 18, 1960 United States. Patent O 3 142 336 METHOD AND APPRTUS Fon INJECTING STEAM ENT() SUBSURFACE FORMATONS Todd M. Doscher, Beilaire, Tex., assigner to Shell 011 Company, New York, N.Y., a corporation of Delaware Filed July 13, 1960, Ser. No. 43,463 6 Ciaims. (Cl. 166-11) This invention relates to the producing of oil from underground formations and pertains more particularly to a method land apparatus `for treating an oil-bearing formation through an injection well to reduce the viscosity of the oil in the formation and drive it to a producing well in communication with the same formation.

The producing formations of many oil fields contain low-gravity oil whose viscosity is of a value high enough to prevent easy flow of the oil through the formation and into a well. In some fields of this type, steam ocding of the producing formation is carried out through one or more injection wells in order to reduce the viscosity of the production fluid and drive the heated oil to adjacent wells, in the same field, through which it is produced to the surface.

An oil -well is provided with a casing extending from the top of the lwell down to at least the top of the producing formation and generally Ibelow the producing formation in order to line the well. Prior to perforating the well casing opposite the oilproducing formation, the casing of -a steam injection well is cemented at a level immediately above the oil producing formation and also preferably immediately below the oil-producing formation in order to block the intrusion `of water from other formations and to prevent the escape of steam vertically along the surface of the well casing to other formations. Cement between a rwell casing and the wall of a well forms an effective fluid-tight seal against the passage of fluids thereby. However, steam injection wells are subjected to high temperatures which often cause differential expansion of the well casing and cement which results in a failure of the casing-cement bond, thus providing a path by which steam can escape to the surface and thereby destroy the effectiveness of the steam liood operations.

It is therefore a primary object of the present invention to provide fa method and apparatus for treating an oilbearing formation with steam through an injection well while preserving the casing-cement bond outside the casing to prevent the escape of steam to the surface or the intrusion of water from ladjacent formations.

A further object of the present invention is to provide apparatus whereby steam may be efficiently caused to flow down a well .and be injected into an oil-bearing formation to reduce the viscosity of the oil in the formation and drive it to other adjacent wells.

Another object to the present invention is to provide apparatus 4for steam injection through wells wherein the packing elements used therein are cooled during operations -by circulating water.

Still another object of the present invention is to provide steam injection well apparatus including packer elements wherein the steam pressure on one side of the packer elements is substantially counter-balanced by circulating water under pressure on the other side thereof to keep to a minimum the differential pressure across the packer elements.

These and other objects yof this invention will be understood from the following description taken with reference to the drawing, wherein:

FIGURE l isa diagrammatic view taken in longitudinal crossasection of la steam injection well installation in accordance with the present invention, and,

FIGURE 2 is ya diagrammatic View which forms the 3,142,336 Patented July 28, 1964 ICC downward extension of the apparatus illustrated in FIG- URE l.

Referring to the drawing, a well casing 11-12 is shown as comprising a length of large-diameter casing 11 connected to a length of small-diameter casing 12 by means of a reducer coupling 13 of any suitable type. Although the casing -is made up of sections of pipe of different diameter it will be considered as a single element for purposes of the present invention. The well casing 11-12 lis cemented in the well in 'any suitable manner well known to the art. An expansion joint 21 is installed in the casing 12 to prevent compression failure of the casing 12 due to thermal expansion. Accordingly, the casing 12 is fixed in position at the bottom of the well bore to prevent formation fill from dropping under casing 12 and injuring associated downhole equipment during alternate heating and cooling cycles. The lower end of the well casing 12 within the oilaproducing zone, such 'as the section of casing below coupling 16, is perforated in any suitable manner to permit the escape of steam from the casing.

At a level near the top of the oil-producing formation the well casing 12, before being lowered into the well, was provided with a metal petal basket 17 positioned below a cementing oat collar of any suitable type represented Iby ports 18 in the well casing 12. During cementing operations cement is circulated either down through the casing 11 or through a special cementing string (not shown) to be discharged through the ports 18. The metal basket 17 prevents the downward flow of cement which is forced to liow upwardly in the annulus between the well casing 11 and the borehole wall 15 yto form a sheath of cement 2t? which forms an effective seal preventing the escape of steam to the surface or the intrusion of water into the borehole. It is not essential, however, that the cement sheath 2t) extend all the way to the surface of the earth.

Suspended concentrically within the well casing 11-12 is a tubing string 22 extending from the surface of the earth down to a point in the lower end of the casing 12 where perforations 19 are provided for the escape of steam into the formation, and an intermediate casing or pipe string 23 which extends from the surface of the earth preferably down `to a point substantially level with the top of the oilaproducing formation. The lower end of the pipe string 23 and a predetermined portion of the tubing string 22 are welded to al closure or sealing assembly housing 24 which is provided with packer elements 25 and 26 mounted on a packer mandrel 27. The packer Kand seal assembly 24 is adapted to seat on shoulder 28 within the well casing 11 and seal the outer annular space 31 between the well casing and the pipe string 23 when the ring 29 below the packer element 26 seats on the shoulder 28 and is moved upwardly shearing pins 29a, moving axiallyslidable ring 26a upwardly and compressing packer elements V25 and 26 which expand outwardly in sealing position as ring 25a, threaded to mandrel 27 above packer element 25, remains stationary. By welding this seal assembly 24 to the outside of the pipe string 23 and the tubing string 22 at points 23a and 22a, respectively, a sea-l is provided for the inner annular space 32 formed between the pipe string 23 and the tubing 22. The packer and seal assembly 24 is also preferably provided with spring-loaded hold-down slips 33 which are designed to engage cooperating serrated elements or hold-down threads 34 formed on the inner surface of the well casing 11 just above the reducer coupling 13.

The top of the well installation illustrated in the drawing is closed in any suitable manner. For example, in the arrangement shown a ange 3S is Welded to the casing string 11. The intermediate pipe string 23 in turn is welded to a mating ange 36 which, when positioned on ange 35 closes the annular space 31 yat the top thereof.

In turn, a tubing head or cap 37 is threadedly connected to the top of the intermediate pipe string 23 to close the annular space 32 between the pipe string 23 and the tubing string 22. The packing within the tubing head 37 is of any suitable type such for example as asbestos or braided copper packing which is suitable of withstanding temperatures up to 1200 F.

The port in the tubing head 37 provides means by which a pipe communicates with the inner annular space 32 between the tubing string 22 and the pipe string 23. The upper flange 36 in turn is provided with a flow conduit 41 in communication with the outer annular space 31. Suspended from the closure flange 36 and extending downwardly in the outer annular space 31 to a point just above the packer elements 25 and 26 is a small-diameter water line 42. It is to be noted that the annular space 31 extends downwardly within the mandrel 27 0n which the packer elements are mounted thus providing a flow passage for cooling the mandrel and the packer elements mounted thereon. If desired, during cementing operations the seating shoulder 28 on the casing 11 and the hold-down threads 34 formed thereon may be covered by a removable seat protector (not shown) which is secured to seal assembly 24 by secondary thread 43.

In the operation of the method of the present invention by use of the apparatus illustrated in the drawing and described hereinabove, steam is injected from a suitable supply source (not shown) into the tubing string 22 at the top of the well and is owed down the tubing string to be discharged from the lower end thereof and thence through the perforations 19 and the casing string 12 from where it `flows into the oil producing formation between the cement plugs 14 and 20 in the borehole. At the same time the pipe 4l) in communication with the inner annular space 32 outside the tubing string 22 is connected to a source of vacuum (not shown) and a partial vacuum is created within the inner annular space 32 to decrease the convection heat losses to the pipe string 23 and the outer casing 11. Simultaneously, cooling water is circulated down the small-diameter water pipe 42 to be discharged from the lower end thereof near the bottom of the outer annular space 31 and near the packer elements 25 and 26. Water at the bottom of the annular space 31 flows upwardly and is discharged out the Water discharge pipe 41 at the top of the well. It is apparent that the flow of the cooling water could be reversed but it is preferred that it be injected into the well through pipe 42. The pressure of the circulating cooling water is selected at a value so as to keep to a minimum the differential pressure across the packer elements 25 and 26, thus minimizing any chance of failure of the packer elements. To further reduce radiation heat losses from Ithe inner tubing string 22, the inner surface of the intermediate pipe string 23 and the outer surface of string 22 is preferably lined or clad with a reflective material such as aluminum.

I claim as my invention:

1. In an oil-bearing formation traversed by an injection well and a producing well in communication with the same formation, and wherein said injection well is equipped with a cemented well casing in open fluid communication with the oil formation and an intermediate concentric pipe string and an inner tubing string within the casingforming inner and outer annular spaces extending substantially to said oil formation with a water line extending down the outer annular space and the tubing string being in open communication with the casing at the level of the oil formation, the methodof treating said oilbearing formations comprising flowing steam down said tubing string, injecting said steam into the oil formation for a time and at a pressure sufficient to reduce the viscosity of said oil and force it to a producing well in communication with the same oil formation, reducing the convection heat loss from said tubing string by creating a partial vacuum on said inner annular space, reducing heat loss from said tubing string by circulating cooling water in and out of said outer annular space to prevent thermal expansion of said casing.

2. In an oil-bearing formation traversed by an injection well and a producing well in communication with the same formation, and wherein said injection well is equipped with a cemented well casing in open iluid cornmunication with the oil formation and an intermediate concentric pipe string and an inner tubing string within the casing forming inner and outer annular spaces extending substantially to said oil formation with a water line extending down the outer annular space and the tubing string being in open communication with the casing at the level of the oil formation, the method of treating said oil-bearing formations comprising flowing steam down said tubing string, injecting said steam into the oil formation for a time and at a pressure suicient to reduce the viscosity of said oil and force it to a producing well in communication with the same oil formation, reducing the convection heat loss from said tubing string by creating a partial vacuum on said inner annular space, reducing the radiation heat loss from said tubing string and circulating cooling water in and out of said outer annular space to prevent thermal expansion of said casing.

3. A method of treating a subsurface oil-producing formation with steam to reduce the viscosity of the oil therein and drive said oil to at least one adjacent producing well, said method comprising the steps of installing in a well a string of well casing extending from the top thereof to at least the top of said oil-producing formation, sealing the space between the outside of said casing and the well wall at least near the top of said oil producing formation, installing within said casing a concentric intermediate pipe string extending to a level at least below a portion of the sealed space and simultaneously installing within said pipe string a tubing string in open communication with the casing at a level opposite the oil-producing formation with the space between the casing and the tubing string being sealed at the bottom of the pipe string to form inner and outer annular spaces around said tubing string, installing within said outer annular space a water line extending close to the bottom thereof, closing the tops of said inner and outer annular spaces while providing communication therewith, circulating cooling water down said water line and up the outer annular space, creating a vacuum within the inner annular space, and flowing steam down said tubing string and into said oil-producing formation.

4. A method of treating a subsurface oil-producing formation with steam to reduce the viscosity of the oil therein and drive said oil to at least one adjacent producing well, said method comprising the steps of drilling a well into an oil-producing formation, installing a string of well casing in said well extending from the top thereof to at least the top of said oil-producing formation, sealing the space between the outside of said casing and the well wall at least near the top of said oil-producing formation, installing within said casing a concentric intermediate pipe string extending to a level at least below a portion of the sealed space and simultaneously installing within said pipe string a tubing string in open communication with the casing at a level opposite the oil-producing formation with the space between the casing and the tubing string being sealed at the bottom of the pipe string to form inner and outer annular spaces around said tubing string, installing within said outer annular space a water line extending close to the bottom thereof, closing the tops of said inner and outer annular spaces while providing communication therewith, circulating cooling water down said water line and up the outer annular space, creating a vacuum within the inner annular space, flowing high pressure steam down said tubing string and into said oilproducing formation, and continuing the injection of the steam into the formation to reduce the viscosity of the oil and force it to a producing well in communication with the same formation.

5. Apparatus for injecting steam into an oil-producing formation through a well drilled thereinto, said apparatus comprising a well casing extending from the surface downwardly into at least the top of the oil formation yand sealed in the well atleast at one point above said oil formation, perforations in said well casing opposite said oil formation, a tubing string suspended within said casing and extending to the level of the oil formation Iand in open communication with the casing at said level, an intermediate concentric pipe string between said tubing string and said casing forming inner and outer annular spaces extending substantially to the top of said oil formation, seal means closing the lower ends of said inner and outer annular spaces, closure means at the top of the well for closing said inner and outer annular spaces, rst port means through said closure means in communication with said inner annular space by which a partial vacuum to said space may be applied, second port means through said closure means in communication with said outer annular space for passing cooling water therethrough, and ow conduit means suspended from said closure means in said outer annular space substantially to the bottom thereof for circulating cooling water therethrough.

6. Apparatus for injecting steam into an oil-producing formation through a well drilled thereinto, said apparatus comprising a well casing extending from the surface downwardly through at least the top of the oil formation and sealed in the Well at least at one point above said oil formation, perforations in said well casing opposite said oil formation, a tubing string suspended within said casing and extending to the level of the oil formation and in open communication with the casing at said level, and intermediate concentric pipe string between said tubing string and said casing forming inner and outer annular spaces extending substantially to the top of said oil formation, seal means closing the lower ends of said inner and outer annular spaces, cooperating anchoring means carried by said casing and said intermediate pipe string for anchoring said pipe string, an expansion joint in said casing opposite the oil formation, closure means at the top of the well for closing said inner and outer annularspaces, first port means through said closure means in communication with said inner annular space by which a partial vacuum to said space may be applied, second port means through said closure means in communication with said outer annular space for passing cooling water therethrough, and flow conduit means suspended from said closure means in said outer annular space substantially to the bottom thereof for circulating cooling water therethrough.

References Cited in the iile of this patent UNITED STATES PATENTS 895,612 Baker Aug. 11, 1908 1,413,197 Swan Apt. 18, 1922 2,341,573 Reed Feb. 15, 1944 2,584,606 Merriam et al Feb. 5, 1952 2,929,451 Hurlstone et al Mar. 22, 1960 

1. IN AN OIL-BEARING FORMATION TRAVERSED BY AN INJECTION WELL AND A PRODUCING WELL IN COMMUNICATION WITH THE SAME FORMATION, AND WHEREIN SAID INJECTION WELL IS EQUIPPED WITH A CEMENTED WELL CASING IN OPEN FLUID COMMUNICATION WITH THE OIL FORMATION AND AN INTERMEDIATE CONCENTRIC PIPE STRING AND AN INNER TUBING STRING WITHIN THE CASING FORMING INNER AND OUTER ANNULAR SPACES EXTENDING SUBSTANTIALLY TO SAID OIL FORMATION WITH A WATER LINE EXTENDING DOWN THE OUTER ANNULAR SPACE AND THE TUBING STRING BEING IN OPEN COMMUNICATION WITH THE CASING AT THE LEVEL OF THE OIL FORMATION, THE METHOD OF TREATING SAID OILBEARING FORMATIONS COMPRISING FLOWING STEAM DOWN SAID TUBING STRING, INJECTING SAID STEAM INTO THE OIL FORMATION FOR A TIME AND AT A PRESSURE SUFFICIENT TO REDUCE THE VISCOSITY OF SAID OIL AND FORCE IT TO A PRODUCING WELL IN COMMUNICATION WITH THE SAME OIL FORMATION, REDUCING THE CONVECTION HEAT LOSS FROM SAID TUBING STRING BY CREATING A PARTIAL VACUUM ON SAID INNER ANNULAR SPACE, REDUCING HEAT LOSS FROM SAID TUBING STRING BY CIRCULATING COOLING WATER IN AND OUT OF SAID OUTER ANNULAR SPACE TO PREVENT THERMAL EXPANSION OF SAID CASING. 